Wireless Local Area Networks (LAN) have become a popular alternative to wired LANs, especially at locations where wiring is difficult or costly. For example, a warehouse or a hospital that was not built to include a wiring infrastructure for the LAN may have great difficulties to accommodate a wired network. The cost for adding the wiring infrastructure into such a building may be prohibitively higher than deploying a wireless LAN.
Stations or devices in a wireless LAN may communicate with each other directly over wireless channels, or indirectly through a wireless Access Point (AP). A wireless AP may act as a hub to provide connectivity for the devices associated with the AP, or may serve as a bridge to connect a wireless LAN to a variety of wired networks, e.g., Ethernet and Token Ring networks. A number of wireless APs may be interconnected to provide an extensive coverage area for a wireless LAN.
There are several approaches to implementing an AP. An AP may be implemented as an embedded hardware product, or as a software product that may be run on a general-purpose computer. The APs that are implemented in software may be called soft APs.
One widely-accepted industry standard for wireless LANs is the IEEE 802.11 standard published in 1997. The IEEE 802.11 standard specifies that a device in a wireless LAN enter a power-saving state after being inactive for a pre-determined period of time. The device may periodically wake up from the power-saving state to receive beacon signals from the AP with which the device is associated. The beacon signals may indicate whether there are messages waiting for the device at the AP.